docs: def get_agreement(self, agreement_id):
          """
          Retrieve the agreement for a agreement_id.
  
          :param agreement_id: id of the agreement, hex str
          :return: the agreement attributes.
          """
          agreement = self.contract_concise.getAgreement(agreement_id)
          if agreement and len(agreement) == 6:
              agreement = AgreementValues(*agreement)
              did = add_0x_prefix(agreement.did.hex())
              cond_ids = [add_0x_prefix(_id.hex()) for _id in agreement.condition_ids]
  
              return AgreementValues(
                  did,
                  agreement.owner,
                  agreement.template_id,
                  cond_ids,
                  agreement.updated_by,
                  agreement.block_number_updated
              )
  
          return None